NEVER use the Hint button during your entire playthrough. This will make the game a tad more challenging, but not much. The game revolves around collecting "hidden items" and using them in the correct place to progress through the story. Objects with a little blue puzzle piece on them require the use of one of more objects to solve. The game gives you a fairly substantial clue just by clicking on these items with the blue puzzle piece on them. Most items that are definitely related to the story will sparkle making them easier to see. See the first section of the guide (Story Related Achievements) for some general solutions to the games many puzzles.